A Chinese teacher has been sent to a labour camp over his internet photographs of schools that collapsed in the Sichuan earthquake, a rights group said today.

Liu Shaokun was ordered to serve a year of "re-education through labour", according to Human Rights in China. The system does not require a formal charge or criminal trial and there is no appeal.

He is believed to be the third person held after posting material questioning why so many schools were destroyed in the May 12 earthquake, in which around 70,000 people died.

Scores of schools across the south-western province collapsed following the 7.9 magnitude shock. In many cases, other buildings around them remained intact, prompting questions about the quality of their construction.

The authorities initially responded to a wave of public outrage by promising an inquiry into whether shoddy building work was linked to corruption.

But they have subsequently silenced critics, ordering the state media notto report on the subject and preventing parents from protesting.

In recent weeks, police have dragged grieving relatives away from demonstrations in some areas. Families have been pressed to sign contracts granting them compensation, which include commitments not to protest or attempts to sue the authorities.

"Instead of investigating and pursuing accountability for shoddy anddangerous school buildings, the authorities are resorting to re-educationthrough labour to silence and lock up concerned citizens like teacher LiuShaokun and others," said Sharon Hom, executive director of Human Rights in China.

The group said that Liu, a teacher at Guanghan middle School in Deyang City, was detained on June 25 for "disseminating rumours and destroying social order". His wife, who has not been allowed to see him, was told last week that he had been sent to a labour camp.

He had travelled through the quake zone taking pictures of the ruins ofschools and circulating them on the internet, along with criticism ofshoddy building work.

The public security bureau in Deyang told the Guardian it was trying tofind out more about the matter and the propaganda department of theGuanghan City people's government said it had not heard of the case.

But an official with the general office of the Guanghan school where Liuworked told Reuters: "He was detained late last month by people fromnational security bureau for deliberately inciting families of victims topetition and disseminating anti-government rumours. They searched his home and found evidence."

China uses the labour camps to detain suspects for up to four years. Critics say it is unfair and is used to detain politicaland religious activists.

The family of Huang Qi, a long-standing human rights activist from Sichuan, said this month that he had been formally arrested for "illegal possession of state secrets" after helping bereaved parents and posting articles about structural failings of schools on his website.

His wife, Zeng Li, told reporters he had not been allowed to see a lawyer or relatives since his detention on June 10.

One of his articles was about the detention of Zeng Hongling, a formeracademic detained on subversion charges after she posted online essays attacking shoddy construction, according to the Hong Kong-based Information Centre for Human Rights and Democracy.